Frag The Cullen forwarded to me a film clip made by Jihaku of a Team Slayer game played a few days ago. In that game, player Geo Stelar seems to have an infinite bag of bubble shields. No matter how many times he deploys it, he always has another, a fact he uses to his advantage in this film. There's also a thread about the alleged exploit at Bungie.net.

It's quite definitely identified as a team slayer game and not a Forge or a Custom film, so that would seem to rule out those ways of altering the behavior of the bubble shield.

Have hackers already been able to modify Halo 3 maps and use those modified maps in matchmaking? Is this a bug in the game? An artifact of extreme lag? The last theory might be the best; the clip author Jihaku seems to die after deploying a bubble shield, but then drops one when he shouldn't have had one. Geo Stelar picks up that bubbleshield, and shortly after realizes that it doesn't disappear from his inventory when deployed.